G2/M accumulation in prostate cancer cell line PC-3 is induced by Cdc25 inhibitor 7-chloro-6-(2-morpholin-4-ylethylamino) quinoline-5, 8-dione (DA 3003-2).

Cdc25 phosphatases are dual-specific phosphatases that play a role in cell cycle progression. In many human cancers, Cdc25 phosphatases are overexpressed as compared with normal tissues. In addition, overexpression of Cdc25 phosphatases in prostate cancer is correlated with disease progression. The antiproliferative efficacy of Cdc25 phosphatase inhibitor 7-chloro-6-(2-morpholin-4-ylethylamino) quinoline-5, 8-dione (DA 3003-2) was investigated in the PC-3 asynchronous human prostate cancer cell line using a cell-based assay. The time course changes in cell cycle distribution and the modulation of cell cycle regulators after DA 3003-2 administration were analyzed using the MTT assay. We found that the relative IC(50) of DA 3003-2 was 2-fold lower as compared with its congener (2-mercaptoethanol)-3-methyl-1, 4-naphthoquinone (NSC 672121). Asynchronous PC-3 cells accumulated in the G2/M phase at 24 h after treatment with 10 μM DA 3003-2 or 20 μM NSC 672121, which represent IC(70) concentrations. Treatment of cells with DA 3003-2 caused hyperphosphorylation of Cdc2 tyr(15) in cyclin B(1) and cyclin A complexes. DA 3003-2 did not downregulate the protein expression levels of Cdc25s, cyclins and cyclin-dependent kinases (Cdks). To conclude, after DA 3003-2 administration asynchronous PC-3 cells accumulated in the G2/M phase, with hyperphosphorylation of the G2/M cyclin-Cdk complex.